1. Field of the Invention
This invention is related in general to the field of medical devices for drug infusion and, in particular, to hypodermic syringes.
2. Description of the Related Art
In the process of using hypodermic needles it has become increasingly important to avoid accidental pricking of care providers which might result in the transmission of serious diseases. Thus, devices have been developed to protect a user by retracting the needle into the syringe after a hypodermic injection is performed.
The prior art describes hypodermic syringes comprising a cylinder with an end portion over which a hypodermic needle is releasably arranged, a piston slidably displaceable in the cylinder, and coupling means connected to the piston and co-acting with the hypodermic needle for connecting the piston and the hypodermic needle. Such a hypodermic syringe is described in U.S. Pat. No. 4,950,241.
In a known hypodermic syringe, a connecting piece is placed in the hypodermic syringe for coupling the piston with the hypodermic needle. During use, a needle with a hub is pushed onto the syringe in the usual manner, whereby the hub and the channel of the needle connect therein with the connecting piece. After injecting, the piston is coupled to the connecting piece by means of a coupling member and when the piston is retracted the connecting piece and the needle and hub placed thereon are pulled inside.